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Fluid Journal : Fluid Journal 2005-2007
Early Spring 2006 Applying Some Starter N at Seeding Critical in Spring Wheat and Canola Drs. G. Lafond, S. Brandt, W. May, C. Grant, A. Johnston Summary: The results for our Indian Head site showed that a minimum of 33 percent of the total nitrogen (N) fertilizer required should be applied at seeding time to assure that none of the yield potential is lost. However, to further minimize the risks of losing any yield potential, we speculate that as high as 50 percent of the total N required should be applied at seeding. The proportion will be dictated by the agro-ecological zone. With spring wheat, applying the N as late as the 5- leaf stage did not appear to reduce grain yields. With canola, applying N as late as the start of flowering did not affect grain yields. Canadian researchers speculate that 50 percent of total N required should be applied at seeding to minimize risks with postemergent N applications. Fluid Journal 1 When the increasing need for environmental sustainability is combined with increasing demands for food and fiber and current global trade policies and then all of that is superimposed on the need for producers to remain economically viable, attention has to be focused on efficiencies at all levels of the production cycle. The current high prices of oil and natural gas have resulted in substantially higher nitrogen (N) fertilizer prices. This has a direct impact at the farm gate because N fertilizers represent a significant portion of the overall variable cropping costs and account for over 65 percent of all energy requirements to grow a crop. These factors are stimulating agronomic questions on how to improve N-use efficiency (NUE) and the management required to attain higher efficiencies. It is well recognized that the highest Figure 1. The effect of N timing and starter N levels on yield (average bu/A) of spring wheat at Indian Head, 2004. efficiencies for N fertilizer are obtained when N fertilizers are applied as close to crop needs as possible, reducing the opportunity of losses through leaching, denitrification, and immobilization. A number of studies were conducted in the last few years to examine more closely the merits of postemergent N applications using UAN solutions and surface dribble applications as a way to apply N closer to the time of crop needs. The studies showed that this approach was very feasible but it was not without risk and was never better than applying all the fertilizer at the time of seeding as is currently practiced in a one-pass, no-till seeding and fertilizing system. The studies concluded that the unpredictability of rainfall increases the risks of surface dribble bands because some rainfall is required to move the fertilizer into the soil. In 2003, where no significant rainfall was experienced for the critical part of the growing season, yield losses were experienced with post-emergent N applications due to the inability of the crops to access the N stranded at the surface. The studies also showed that even when a coulter was used to place the fertilizer in the soil in a year like 2003, the yield potential was still not regained. In situations of adequate and timely rainfalls, the coulter provided no advantages over the surface dribble bands. The conclusion was that some N would need to be applied at time of seeding and the proportion would more than likely be greater than 33 percent of the recommended N needs. There is also an urgent need to determine the latest crop stage feasible for applying the N fertilizer without jeopardizing the crop's yield potential. The other important aspects of this approach deal with risk management of N applications, especially in the drier
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